Introduction to Multiple Oracle Homes and OFA

When you install an Oracle database, you are installing one of the largest applications that your computer can support. Using multiple Oracle homes and OFA provides many advantages when administering large databases. The following advantages are the most important:

Structured organization of directories and files and the consistent naming used for database files simplify database administration.

Distribution of I/O across multiple disks prevents performance bottlenecks caused by multiple read or write commands issued simultaneously to a single drive.

Distribution of applications across multiple disks safeguards against database failures.

Login home directories are not at risk when database administrators add, move, or delete Oracle home directories.

Multiple versions of application software can execute concurrently.

Software upgrades can be tested in an Oracle home in a separate directory from the Oracle home where your production database is located.

Oracle homes also have a name associated with them, which you specify along with their location during installation.

Benefit of Using Multiple Oracle Homes

The main benefit of using multiple Oracle homes is that you can run multiple releases of the same products concurrently. For example, you can test an Oracle9i Release 1 (9.0.1) database patch before you run your production database Oracle9i Release 1 (9.0.1) against it.

Multiple Oracle Home Functionality in Different Releases

Modifications to multiple Oracle home functionality have occurred since it was introduced in Oracle8 release 8.0.4. This section helps you determine the capabilities of your Oracle home depending on the release you are using.

Oracle8 Releases Before 8.0.4

Releases of Oracle for Windows NT and Windows 95 prior to Oracle8 release 8.0.4 support only single Oracle homes, allowing you to install and run Oracle products in a single Oracle home. Different releases of Oracle products can be installed in the same Oracle home provided they have different first or second-digit release numbers. For example, you can install Oracle7 release 7.2 products and Oracle7 release 7.3 products or Oracle7 release 7.x and Oracle8 release 8.x products in the same Oracle home. However, you cannot install multiple third-digit releases of the same products. For example, you cannot install Oracle7 release 7.3.2 and Oracle7 release 7.3.3 products on the same computer; one installation will overwrite the other.

Oracle8 Releases 8.0.4 to 8.0.6

You can install one or more releases of Oracle products in multiple Oracle homes. For example, with multiple Oracle homes, you can install Oracle8 release 8.0.x and Oracle8i release 8.1.3 products or Oracle7 release 7.x and Oracle8 release 8.0.x products in different Oracle homes on the same computer.

You can also install different releases of Oracle products in the same Oracle home provided they have different first or second-digit release numbers. For example, you can install Oracle7 release 7.2 products and Oracle8 release 8.0.x products in the same Oracle home.

Oracle8i Release 8.1.3 to Oracle9i Release 1 (9.0.1)

These releases have the same multiple Oracle home functionality as Oracle8 releases 8.0.4 to 8.0.6, but the following restrictions apply:

You cannot install any release from Oracle8i release 8.1.3 to Oracle9i Release 1 (9.0.1) into an Oracle home that was created using the old installer. (The old installer was called Oracle Installer and was used for installations before Oracle8i release 8.1.3; the new Java-based installer is called Oracle Universal Installer.)

You cannot install releases prior to Oracle8i release 8.1.3 into an Oracle home that was created by any release from Oracle8i release 8.1.3 to Oracle9i Release 1 (9.0.1).

Releases from Oracle8i release 8.1.3 to Oracle9i Release 1 (9.0.1) must be installed in separate Oracle homes. You cannot have more than one release installed in each Oracle home.

Oracle8i Release 8.1.5 to Oracle9i Release 1 (9.0.1)

You can use an Oracle9i Release 1 (9.0.1) listenerto spawn a connection to a database from Oracle9i Release 1 (9.0.1), Oracle8i release 8.1.x, Oracle8 release 8.0.x, or Oracle7 release 7.3.x. Some restrictions apply, however, in using Oracle9i Release 1 (9.0.1) listeners with the earlier releases of the database:

You should enable process mode external procedures for Oracle9i Release 1 (9.0.1) if you want to spawn a connection to a Oracle8 release 8.0.3 database.

You must install the Oracle8 release 8.0.4.0.3 (or later) patch for Oracle Net.

You cannot enable shared sockets.

WARNING:

Multiple Oracle homes functionality works only with Oracle8 releases 8.0.4 and later. For example, if you have Oracle7 release 7.3.3 products already installed on your computer, then it does not work. You cannot install Oracle7 release 7.3.4 products in a separate Oracle home.

One-Listener Support of Multiple Oracle Homes

You can use one listener for spawning connections to databases for multiple Oracle homes. Simply add each system identifier to the SID_LIST section in the ORACLE_BASE\ORACLE_HOME\network\admin\listener.ora file.

Because the SID is unique to a system across different Oracle homes, the listener can spawn the database thread for a specific SIDin the correct Oracle home, and the ORACLE_HOMEparameter (used in UNIX environments only) is not needed in the listener.ora file.

Note:

There may be multiple listener.ora files on your computer, one for each Oracle home. To ensure that you use the correct listener.ora file, check the Oracle home name in the listener service. See "Managing Oracle Services" in Oracle9i Database Administrator's Guide for Windowsfor information on verifying service names.

Multiple Oracle Home Environments

This section describes the differences among multiple Oracle home environments since they were first introduced in Oracle8 release 8.0.4.

Oracle Home Environments in Oracle8 Releases 8.0.4 and Later 8.0.x

If you have Oracle8 release 8.0.4 or later 8.0.x Oracle homes on your computer, then note the differences in Table 6-1 between the first Oracle home you installed and more recent Oracle homes you may install.

Table 6-1 Oracle Home Environments in Oracle8 Releases 8.0.4 and Later 8.0.x

Subkeys for each Oracle home are added in the HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE subkey. For example, the next subkeys after HOME0 are HOME1, HOME2, HOME3, and so on. For more information on the registry keys and subkeys, see Chapter 9, "Configuration Parameters and the Registry" in this manual.

For Oracle8i releases 8.1.3 and 8.1.4, the second database you create on your computer has a SID of ORCL0. For Oracle8i release 8.1.5 and onwards, you must type in the global database name and SID name of your choice when prompted during installation.

1For Oracle8i releases 8.1.3 through 9.0, the SID can be a maximum of 64 alphanumeric characters in length. For all Oracle for Windows releases prior to 8.1.3, the SID is a maximum of 4 alphanumeric characters.

Changing the Value of PATH

Unless you specify otherwise at installation time, the Oracle home in which you installed products most recently is the first directory listed in your PATH (primary home). As such, it has priority over the other Oracle home entries in your PATH.

If you start a product from the MS-DOS command prompt, then the release of the product started is the one in the Oracle home listed first in your PATH, unless you specifically start a different release of the product by one of the following methods:

Specifying the full directory path name to the release of the product you want to use at the MS-DOS command prompt

Changing to the directory that contains the executable you want to use

Changing your PATH so that the first entry points to the binary files for the product release you want to use

You can change the value of PATH by using one of the following methods:

You can assign a new value at the MS-DOS command prompt. The new value reverts to its previous value when you quit the session.

Note:

The first two methods of changing the value of PATH are only valid if you are a member of the Administrators group. After you have changed the value of PATH, you must open a new MS-DOS command prompt window to make it active. The change is not reflected in already-opened windows.

Using Oracle Home Selector

Oracle Home Selector is a graphical user interface tool that enables you to edit your environment path to make an appropriate Oracle home directory your primary home. This tool can be used only when you have multiple, active Oracle home directories on a single computer.

Select the Oracle home that you want as the primary Oracle home from the drop-down list.

Click OK.

At the System Level on Windows NT

Choose Start > Settings > Control Panel.

The Control Panel window appears.

Double-click the System icon.

The System Properties window appears.

Click the Environment tab.

The system variables appear.

Edit the value of PATH in the Value field and choose Set.

Click OK.

At the System Level on Windows 95 or 98

Open the autoexec.bat file.

Edit the value of the PATH statement.

Restart your computer.

In some cases on Windows 95 and Windows 98, the Oracle Home Selector fails to switch the entries in the PATH environment variable as desired. This occurs where the PATH is defined in multiple places in the file autoexec.bat.

For example, if the following lines exist in autoexec.bat:

PATH C:\windows
PATH D:\oracle\ora817;D:\oracle\ora816;%PATH%

then an attempt to switch the order of D:\oracle\ora817 with D:\oracle\ora816 in the PATH using Oracle Home Selector fails.

To work around this limitation, modify autoexec.bat so that the PATH is defined in one location in the file. Using the previous example, modify autoexec.bat to read:

PATH D:\oracle\ora817;D:\oracle\ora816;C:\windows

If you then attempt to use Oracle Home Selector to switch the order of Oracle homes in the PATH, it will succeed.

At the MS-DOS Command Prompt

At the MS-DOS command prompt, enter:

C:\> set PATH=PATHNAME;%PATH%

where PATHNAME is the full path to the binary files for the products you want to use. This change is valid for the current session only. If you want to change the value of your PATH permanently, then use Oracle Home Selector or change the value of PATH at the system level. Both methods are described earlier in this section.

Exiting Oracle Universal Installer After Entering Name and PATH

If you have to exit Oracle Universal Installer unexpectedly after you have entered the name and path for an Oracle home (for example, because there is no more disk space in the path you specified), then you cannot specify a different path until you delete the HOMEID key and the IDx key corresponding to that Oracle home from the registry. To do this:

Read the value of the ORACLE_HOME_NAME parameter for each HOMEID subkey in the HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE key until you find the value that matches the name of the Oracle home you must delete.

Delete the HOMEID subkey you just located.

Delete the appropriate IDx subkey in the HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\ALL_HOMES key, where x has the same value as the ID in HOMEID. For example, if the HOMEID subkey for the home name you want to delete is HOME1, then the appropriate IDx subkey is ID1.

Setting Variables in the Environment or the Registry

Variables set in the environment always override the value of equivalent variables set in the registry. The following section describes the consequences of setting two of the most commonly-used environment variables, ORACLE_HOME and TNS_ADMIN.

ORACLE_HOME

Oracle Corporation recommends that you never set the ORACLE_HOME environment variable, because it is not required for Oracle products to function properly. If you set the ORACLE_HOME environment variable, then Oracle Universal Installer will unset it for you. Oracle products find the value of ORACLE_HOME at the location specified by the ORACLE_BASE\ORACLE_HOME\bin\oracle.key file. If you must set ORACLE_HOME in the environment for another reason, then you must take care to run software only from that Oracle home when the variable is set.

When you run an Oracle application from the MS-DOS command prompt, the first executable by that name found in the directory path runs. For example, C:\> sqlplus. Alternately, if you specify a full directory path, then the specified application runs. For example, C:\oracle\ora82> sqlplus.

If you modify the value of PATH using any of the four methods described in the previous section, then you can choose which release of an application is run from the MS-DOS command prompt. In sum, modifying the value of PATH indicates from which Oracle home to run executables at the MS-DOS command prompt, when no full directory path is specified.

Once an Oracle application starts, it looks for all environment variables first in the current environment and second in the registry key for the Oracle home from which the application is running.

The application knows where it is running from by calling Windows to obtain the executable's path name and then parsing the path name to get the directory from which it is running. In the ORACLE_BASE\ORACLE_HOME\bin directory where the executable resides, there is a file called oracle.key. This file specifies where in the registry to look for variables when applications from that particular Oracle home are run.

For example, if you run C:\oracle\ora82\bin\sqlplus.exe, then sqlplus.exe looks in C:\oracle\ora82\bin\oracle.key to find out where to look for its registry variables. If the oracle.key file does not exist (for version 7 and some version 8 Oracle homes), then Oracle uses HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE to locate the registry variables.

In a typical case, there are no Oracle variables (that is, ORACLE_HOME) set in the environment. Any applications run from an Oracle8 release 8.0.5 or later Oracle home look in the oracle.key file in that Oracle home and find their variables (including ORACLE_HOME) in the correct registry key. Likewise for Oracle9i Release 1 (9.0.1), the Oracle home that gets priority depends on the PATH, but regardless of the PATH setting, all the software works correctly.

Consequences of Setting ORACLE_HOME

If you set ORACLE_HOME in the environment, then software run from another Oracle home will not work reliably. The conflict occurs when you set ORACLE_HOME to point to one Oracle home directory, then attempt to run applications from a second Oracle home. These applications first check for any environment variable settings (such as ORACLE_HOME), before checking the registry through the oracle.key file. Because ORACLE_HOME is set, the applications in the second Oracle home attempt to use files in the first Oracle home, causing a conflict.

For example, suppose you have Oracle8 release 8.0.5 installed in C:\orant and Oracle9i Release 1 (9.0.1) installed in C:\oracle\ora90. Suppose further that ORACLE_HOME is set to C:\orant in the environment. If you run an application from C:\oracle\ora90\bin, then that application first looks in the environment for all variables before looking at its oracle.key file. So an application run from your Oracle9i Release 1 (9.0.1) Oracle home runs with ORACLE_HOME=C:\orant. Therefore, anything that the application uses ORACLE_HOME for will be looked for in C:\orant, where it may not exist. Examples include message files (*.msb), SQL scripts (.sql), and any other files opened by the application and based off ORACLE_HOME.

Note that the same behavior occurs on UNIX. If you run an application from Oracle home number 1 with ORACLE_HOME=OracleHome number 2 in the environment, then the same behavior can be observed.

TNS_ADMIN

Oracle software looks for TNS_ADMIN in one location in the registry (depending upon the type of Oracle home installed). If you installed software into the default Oracle home, then any software running from that Oracle home will look in HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE. If you installed a new-style (8.0.4 or later) multiple Oracle home, then the Oracle software looks in HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\HOMEID. (The ALL_HOMES key is used by the installer and plays no role when translating variables.)

The environment always overrides the registry, so if TNS_ADMIN is set in the environment, then that takes precedence over the TNS_ADMIN setting in the registry. No variables should be set in the environment by the Oracle Home Selector except for the PATH.

Optimal Flexible Architecture Overview

Oracle Optimal Flexible Architecture (OFA) is a set of file naming and placement guidelines for Oracle software and databases. It can also be thought of as a set of good habits to adopt when organizing Oracle directories and files on your computer. All Oracle products on CD-ROM are OFA-compliant; that is, Oracle Universal Installer places Oracle products in directory locations that follow the OFA guidelines. Although using OFA is not a requirement, Oracle Corporation recommends that you use it if your database will grow in size, or if you plan to have multiple databases.

The aim of OFA is to prevent an entire class of problems that can occur when you have different releases of Oracle software and multiple, growing databases on your computer. OFA is designed to provide significant benefits:

For example, Oracle Universal Installer now separates Oracle software executables from database files. Previously, database files were placed in ORACLE_HOME\database, a subdirectory of the Oracle home directory that also contained Oracle software.

Using OFA, Oracle Universal Installer puts Oracle software in ORACLE_BASE\ORACLE_HOME and database files in ORACLE_BASE\oradata. Now when you upgrade a database to the latest release, the new Oracle software executables will be placed in a different Oracle home directory. After you judge the upgrade successful, you can easily remove the old Oracle home directory and reclaim space, because the database does not reside there.

Disk contention decreases, because Oracle administration files, binary files, and datafiles that used to be on one disk can now reside in separate directories on separate disks.

Safeguards against disk failures

By spreading files across more than one disk, disk failures impact as little data as possible.

Support for concurrent execution of application software

Multiple releases of application software can run simultaneously, enabling testing and use of a new release of an application before abandoning the previous release. Transferring to a new release after an upgrade is simple for the database administrator and transparent for the user.

Characteristics of an OFA-Compliant Database

An OFA-compliant database has the following characteristics:

Independent subdirectories

Categories of files are separated into independent subdirectories so that files in one category are minimally affected by operations on files in other categories.

Consistent naming conventions for database files

Database files are easily distinguishable from all other files. Files of one database are easily distinguishable from files of another database. Datafiles, redo log files, and control files are easily identifiable. Datafiles are clearly associated with a particular tablespace.

Integrity of Oracle home directories

You can add, move, or delete Oracle home directories without having to revise applications that refer to them.

Separation of administrative information for each database

The ability to distinguish administrative information about one database from that of another ensures a reasonable structure for the organization and storage of administrative data.

I/O loads are tuned across all disks, including disks storing Oracle data in raw devices, if needed.

Differences Between Directory Trees by Release

OFA has necessitated changes to the Oracle database directory tree. This section lists the differences.

Top-Level Oracle Directory

When you install an Oracle8i release 8.1.3 or earlier release, all subdirectories are located under a top-level ORACLE_HOME directory that by default is C:\orant.

When you install an Oracle8i release 8.1.4 or later OFA-compliant database, all subdirectories are no longer under a top-level ORACLE_HOME directory. There is now a new top-level directory called ORACLE_BASE that is of the form X:\oracle where X is any hard drive. If you install an OFA-compliant database using Oracle Universal Installer defaults, then ORACLE_BASE is C:\oracle.

Database Filenames

In Oracle8i release 8.1.3 and earlier releases, database files have the SID in the database filename. For example, the first control file is named ctl1SID.ora.

Beginning with Oracle8i release 8.1.4, database files no longer have the SID in the database filename. For example, the first control file is named control01.ctl. There is no need for the presence of the SID in the filename, because all the database files for a particular database are placed in \oradata under a directory called DB_NAME that is named for that database.

Database Filename Extensions

In Oracle8i release 8.1.3 and earlier releases, all database files have the same .ORA extension.

In an OFA-compliant release, the convention of having .ora as the filename extension for database files is no longer used. Database filenames now have more meaningful extensions. These are:

.ctl for control files,

.log for log files

.dbf for datafiles.

OFA Directory Naming Conventions

OFA uses directory naming conventions that make it easy to identify the precise Oracle home and database name that is associated with a set of files. This section describes the naming conventions used for the top-level directories of an OFA-compliant database directory tree:

ORACLE_BASE Directory

ORACLE_BASE is the root of the Oracle directory tree. If you install an OFA-compliant database using Oracle Universal Installer defaults, then ORACLE_BASE is X:\oracle where X is any hard drive. For example, C:\oracle.

If you are installing Oracle9i for Windows on a computer with no other Oracle software installed, then you can change ORACLE_BASE before running Oracle Universal Installer. Most users will not need or want to do this.

Do not change the value of ORACLE_BASE after you run Oracle Universal Installer for the first time. If there is an existing ORACLE_BASE and you change it, then there will be a conflict of Oracle base directories. If you create another ORACLE_BASE when the original ORACLE_BASE already exists, then certain tools and the database will not be able to find previously created files. They will look for them in the new ORACLE_BASE instead of the original ORACLE_BASE.

Changing ORACLE_BASE at the System Level on Windows NT:

Choose Start > Settings > Control Panel.

The Control Panel window appears.

Double-click the System icon.

The System Properties window appears.

Click the Environment tab.

The System Variables appear.

Select ORACLE_BASE.

Type a new value for ORACLE_BASE in the Value text box, then click OK to exit.

Changing ORACLE_BASE at the System Level on Windows 95 or 98:

Open the autoexec.bat file, using a text editor.

Edit the value of the ORACLE_BASE statement.

Restart your computer.

Note:

An ORACLE_BASE registry key exists for every Oracle home. Ideally, the value of the ORACLE_BASE registry key will be identical for each Oracle home.

ORACLE_HOME Directory

The\ORACLE_HOME directory is located beneath X:\ORACLE_BASE and contains subdirectories for Oracle software executables and network files.

If you install Oracle9i for Windows on a computer with no other Oracle software installed and you use the default settings, then the first Oracle home directory that you create is called \ora90.

ADMIN Directory

Database administration files are stored in subdirectories of ORACLE_BASE\admin\DB_NAME. The names and brief descriptions of some of these subdirectories are:

DB_NAME Directory

DB_NAME is the unique name for a particular database and has the same value as the DB_NAME parameter in the initialization parameter file (init.ora). When you create a database, DB_NAME can be no more than eight characters long and can contain only the following characters:

Alphabetic characters

Numbers

Underscores (_)

Pound sign (#)

Dollar sign ($)

OFA and Multiple Oracle Home Configurations

The following sections describe various OFA and multiple Oracle homes configurations.

Specifying an ORACLE_HOME Directory

To install an OFA-compliant database, you must specify an Oracle home directory in the Path: field of Oracle Universal Installer. It is of the form:

X:\[PATHNAME]\oracle\HOME_NAME

where:

X:\ is any hard drive. For example, C:\

[PATHNAME] is an optional directory path name

\oracle is a mandatory directory path name, unless you changed the value of the ORACLE_BASE registry key before performing the installation

HOME_NAME is the name of the Oracle home

The following are examples of OFA-compliant Oracle home directories:

C:\test\oracle\ora90

D:\oracle\ora90

Installing a Default OFA Database: Example

Install Oracle8i for Windows release 8.l.6 on a computer with no other Oracle software installed and accept the default Oracle Universal Installer settings for the first Oracle home (C:\oracle\ora81) in the path: field.

Complete the installation.

Run Oracle Universal Installer again and install Oracle9i Release 1 (9.0.1). Accept the default Oracle Universal Installer settings for the first Oracle home (C:\oracle\ora90) in the path: field.

Increasing Reliability and Performance

Disk Mirroring

Oracle log files and database files can be separated and treated with different levels of hardware reliability. Oracle log files are highly reliable to start with, because they are stored redundantly. Creating similar reliability for database files may require you to duplicate all of your data, using disk mirrors.

Disk mirroring usually involves two or more identical drives and either a hardware controller or Windows Disk Administrator. If one disk fails, then the other disk(s) can be used to recover data that would otherwise be lost. Using one of the disks to recover lost data may involve "breaking" the mirror. If the mirror breaks, then you must build a new mirror.

Disk mirroring is part of some levels of Redundant Array of Independent Disks (RAID) configurations, provided by the disk controller. The RAID level determines the amount of redundancy. Some RAID levels can use the "hot swapping" feature, which means that you can replace a bad disk with a good one without turning off the computer or losing functionality.

Disk Striping

How you set up disks for use in a database depends on the number of disks and the type of hard disk controllers available. If the hard disk controllers support both striping and mirroring, then Oracle Corporation recommends you configure the controllers to support striping.

Some controllers are configured at system startup time by issuing a keyboard sequence that brings up configuration programs written by the controller manufacturer. One goal is to stripe as many drives together as possible by configuring the controllers. Each stripe shows up as one logical device.

Striping provides significant performance advantages. All the space from the striped drives appears as a single logical drive. Furthermore, the space is used by interlacing "stripes" of space from all of the disks in the stripe. This means that a large file uses some space from the first disk, then some from the second disk and so on to the last disk and then starting back at the first disk again. Each file can be spread over all of the striped disks. The data in such a file may be accessed randomly by more than one CPU without contention.

The controllers that support striping usually provide caching as well. This means that data can be written to the controller and cached and saved for a time in storage not on the disk. Data that is read can be cached on the controller in a similar fashion. Read caching is not necessary for Oracle databases, because all database reads are cached already in the System Global Area. The value of the DB_BLOCK_BUFFERS parameter in the initialization parameter file (init.ora) determines the number of buffers that can be used in the SGA. This value also configures the Oracle9i database on startup.

Using Raw Partitions for Tablespaces

A raw partition is a portion of a physical disk that is accessed at the lowest possible level. The I/O of a raw partition improves performance by approximately 5% to 10% compared to the I/O of a partition containing a file system. Therefore, Oracle Corporation encourages you to use raw partitions for your tablespace files.

Comparison Between OFA on Windows NT and UNIX

You implement OFA on Windows NT and UNIX in the same way. However, differences exist with regard to the following:

Directory Naming

The top-level names of the OFA directory tree differ between Windows NT and UNIX. However, the main subdirectory and filenames are the same on both operating systems.

ORACLE_BASE Directory

On Windows, ORACLE_BASE is associated with an Oracle home directory. ORACLE_BASE is defined in the registry (for example, in HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\HOME0).

On UNIX, ORACLE_BASE is associated with a UNIX user's environment.

Support for Symbolic Links on Windows NT

The goal of OFA is to place all Oracle software under one ORACLE_BASE directory and to spread the files across different physical drives as your databases increase in size.

On UNIX, although everything seems to be in one directory on the same hard drive, files can be on different hard drives if they are symbolically linked or have that directory as a mount point.

Windows NT currently does not support symbolic links, so datafiles will not all show up under a single directory like on UNIX. Instead, you may have oradata directories on multiple drives, with datafiles in each one. In this way, you still get the OFA benefits, even though the datafiles are not all visible in a single directory.

Oracle Corporation recommends that you use one logical drive to store your database administration files and that you place other files, as needed, on other logical drives in an oradata\DB_NAME directory.

In the following example, there are four logical drives for a database named prod:

C:\ contains an Oracle home and the database administration files.

F:\ contains the redo log files. (The F:\ drive could also represent two physical drives that have been striped to increase performance.)

G:\ contains one of the control files and all of the tablespace files. (The G:\ drive could also use a RAID Level-5 configuration to increase reliability.)